1. Field of the Invention
The present invention relates to a novel serotonin antagonist and an anti-platelet agent, more particularly, a serotonin antagonist and an anti-platelet agent which potently and specifically inhibit the serotonin 2 receptor with low adverse side effect.
2. Discussion of the Background
It is believed that the thrombus greatly participates in ischemic disorders such as cardiac infarction and cerebral infarction and, in particular, the platelet plays an important role in the formation of the arterial thrombus. Known anti-platelet agents include arachidonic acid metabolism-inhibiting agents, platelet cyclic nucleoside-related agents, thromboxane receptor antagonists. Aspirin and ticlopidine have also been clinically used. However, the effect of these agents is not sufficient and thus development of more effective agents has been in demand.
It is known that serotonin (5HT), which is stored in .alpha. granules of the platelet, is released by activation of the platelet caused by various stimulations, and the released serotonin increases the calcium ion level in the cell via the serotonin 2 (5HT.sub.2) receptor on the platelet membrane, resulting in aggregation of the platelet. It is believed that the 5HT.sub.2 receptor existing in the vascular smooth muscle participates in the blood vessel contraction. Accordingly, the 5HT.sub.2 receptor antagonist is expected to have vasoconstriction inhibiting activity in addition to the platelet aggregation inhibiting activity and, therefore, may also have potent anti-thrombus function.